Manufacture of safety paper



UNITED STATES PATENT OFFlC E MANUFACTURE OF SAFETY PAPER Viktor-T. Bausch, Berlin, and Adolf Schroth, Nell- Kaliss, Mecklenburg, Germany, assi more Felix Schoeller & Banach, Mecklenburg, Germany No Drawing; Application June 23,1986,.8erial No. 86,888. In Germany February 7, 1934 8 Claims.

This invention relates to the manufacture and production of safety papers, for use in preventing the fraudulent alteration of documents.

It is well known to protect documents from falsification by the use of chemicals by means of safety reagents which react with oxidizing agents to produce discolouration. This discolouration can in general be removed more or less easfly by reducing agents without leaving any trace.

No safety reagent is yet known which reacts with certainty on the reducing agents which are employed in practice. Mercury sulphanilate has,

'it is true, been previously proposed for this purpose, but, apart from the ease with which it decomposes in -a'irand light, this compound is use- .iess because its reaction with reducing agents is extremely weak. That this must be the case is clear from the fact that organic mercury compounds of this constitution are not true salts in the inorganic sense of the word, but are so-called pseudosalts, in which the mercury is also attached by secondary valencies to other atoms. As distinguished therefrom, inorganic salts which can be reduced by mild reducing agents, in particular sulphites, to form substances or elements of diflerent colour are employed according These -respond into the present invention. stantaneously and with certainty to reducing agents, and, therefore, form reliable and practically useful safety reagents for the detection of reducing agents. Complex salts which contain in the outer sphere a component which is reduci ble to a substance or element of different colour can also be employed in accordance with the invention. In these true salts the element to be reduced can be. present both in the kations as well as in the anions. Further, these salts, in addition to their great reacting power, are also distinguished by their stability, and above all by their resistance to decomposition by light. Owing to this stability it is possible to combine these safety reagents with other chemicals, in particular with salts which react on oxidizing agents with the production of discolouration.

Forgers always work with mild reducing agents. These are also the basis of the known commercial erasing liquids. If stronger reducing agents were employed. the paper would also be attacked by them and the forgery would be revealed. 'Sulphite compounds of all kinds are chiefly employed as the reducing agents. The known safety papers, for example those which contain mercury chloride in addition to'salts of nickel and cobalt as well as those which contain bismuth iodide or mercury iodide, do not react at all with such (01. iii-87.95)

The invention also comprises the use of inorganic salts of the kind set forth which, in addition to the reducible constituent, also contain a constituent which reacts with oxidizing agents to produce a discolouration. By this means the manufacture of papers for documents which are 5 to be safeguarded against falsification is greatly facilitated. The salts in-question can be' manufactured by suitable choice of the salt-forming constituent; one such salt, for example, is manganous tellurite.

It is, of course, known to add to safetypapers reagents which respond to oxidizing agents. As distinguished therefrom, however, the safety paper according to the invention possesses the great advantage that, owing to the addition of a salt 16 which responds both to reducing agents and to oxidizing agents, the protection afforded is increased.

The safety reagents according to the invention can be incorporated with the min by precipita- 20 tion during manufacture or can be precipitated Examples 1. Mercury-I-tungstate is precipitated in the hollander in known manner from a soluble mercurous salt by means of alkali tungstate and is so incorporated in the paper pulp to the extent of about 6%. V y

2. Freshly precipitated, still moist barium tellurite is worked up with an oily agent in accordance with methods well known in the print- :5 ing colour art and printed on or applied to the 3. 10% of manganous ferrocyanide is incorporated with the paper pulp by precipitation in the hollander andthe finished paper is subsequently impregnated with a concentrated alkali selenite solution.

4. Manganous tellurite in freshly precipitated condition is incorporated in an amount of about 10% as a suspension with the paper pulp in the hollander.

We claim:

LIn the manufacture of safety paper for the purpose set forth, the step which comprises treating paper material with a reducible inorganic salt ing selected from the group consisting of mantunaztate' and m lelenite.

llnthemanutacture ot safety'paper for-the purpooeaet forth, the stepwhich compriaesin- .corporatinawiththepaperpulparedmiliein- .nltreaistanttodecommllthnbylizht which'upon reduction forms ambatance dlilcrentcolonthantheoriainaiaalt, aaidialtbeinaelectedtromthcmup teliurite, bariumtellurite, mer- I-tunatatcandalkaliaelenite. 3.1a the-manufacture of safety ill-P r for thepurpooeo'etforth,thestepwnich M, D acoaflngcontalningareduclbieinomanlcsaltresistanttouon whichiaotdiii'erentcolortmnthecriaimllalt. saidsfltbeingaelectedtmmfliem ofteliurite,harium-tellurite,mercury- I-mnartateandalhliaelenite.

5.A safety paper for-the purpose set forth w a'mv randasatetyaamt an inorganic salt resistant to flonby light and which upon reduction form: a substance which is oi. diflerent color than the original salt, saidralt being selectedi'rom the group conaistingottelluritqbariumtellm trite, mercury-I-tunastate and alkali s. A method of manuiactu'ring safety m inaccordnncewithciaimLwhereintheinorganic salt is nmrcury- -tunatate.

7. A method of, manufacturing caret paper in accordance with claim 1, wherdn the inorganic salt'is barium 'teliurlte.

8. A method of manufacturing safety Mpcr in accordance with claim 1, wherein the inn organic salt is manganous tellurite. VIK'DOR TH. BAUSCH. 

